Congress gave agencies the approval three years ago to develop phased retirement programs, and it’s taken this long for HUD to unveil its plan.

HUD’s program will be open to non-bargaining unit employees and National Federation of Federal Employees bargaining unit workers who meet eligibility requirements, according to Government Executive. The agency intends to open the phased retirement to rest of its workforce, but can’t say when that will happen.

Those who are eligible will work 20 hours a week and receive half their pay and half their retirement annuity. But at least 20% of their work time has to be devoted to mentoring other employees so someone is in a position to take over once they fully retire.

“The idea is to keep talented employees with valuable institutional knowledge on the job a little longer so they can train other workers, while they also enjoy a partial retirement,” Kellie Lunney wrote at Government Executive.

HUD is not the first federal operation to offer phased retirement. The Library of Congress implemented its program in the spring. The Department of Energy also put rules in place for phased retirement in March, according to Federal News Radio, but it’s unknown if any employees have taken advantage of the plan.